Reducing the diameter of hollow metal articles



F. SINGER March 15,,193gs.

v REDUCING THE DIAMETER OF HOLLOW METAL ARTICLES Filed Feb. 8, 1936 W/TNEJJEJ INVENTOR.

Patented Mar. 15, 1938 UNITED I STATES REDUCING THE DIAMETER F HOLLOW METAL ARTICLES Fritz'Singer, Nuremberg, Germany, assignor to Tubus A. G., Glarus, Switzerland Application February 8, 1936, Serial No. 62,986 In Germany July 2, 1934 13 Claims.

This invention relates to a method of reducing the diameter of hollow metal articles such.

for instance, as tubes.

To reduce the diameter of tubular articles without simultaneous reduction of the wall thickness it has heretofbre been the practice to draw them through a die ring the diameter of the bore of which was smaller than the outer diameter of the tube. For this purpose the ends 1 of the tubes,have to be cold forged to permit the end of the tube to be passed through the die ring and so that it can'be gripped by the drawing tongs. This is disadvantageous because it adds to the cost of the finished product through the added forging operation and the Waste which. unavoidably results from the point, which is useless, except as scrap, when drawing has been completed. Furthermore, long drawbenches are necessary, occupying much space with consequent overhead burdens arising from extensive draw-bench equipment and vfloor space occupied. Another disadvantage is that to a large extent the length of tube that can be drawn is governed by the bench length, and wit is not ordinarily feasible to provide benches long enough to treat great lengths of drawing stock.

It is among the" objects of this invention to provide a method of reducing the diameter of tubes and other hollow metallic articles which is simple, effective, avoids the necessity for forming points on the tubes, is applicable to treatment of long articles, requires only simple and compact apparatus, and embodies other ad- 3 vantages that will appear hereinafter.

The accompanying drawing schematically represents various stages of one complete cycle of the preferred embodiment of the method provided by the invention. a

In accordance with the invention tubular metallic articles are reduced in diameter by 'deflecting the wall of the article toward its longitudinal axis progressively over a relatively short length of the article in a direction toward the unreduced portion, and repeating such incremental reduction along continuously successive short lengths until the diameter of the entire article, or a desired portion thereof, has been reduced. Most suitably this is effected by diereduction using a die having a bore less than that of the article and adapted to produce the desired reduction. Stated in other words, the article is die-reduced progressively in a direction toward the unreduced portion, and after a 55 relatively short length has been thus reduced the reduction is interrupted, and thereafter the cycleis repeated with the next succeeding short lengths of the article to efiect reduction of a desired longitudinal portion of the tube. For reducing without simultaneous reductionof wall thickness the tube is drawn freely, i. e., without a mandrel.

In the practice of the invention, therefore, the tube is supported relative to a die and one is reciprocated toward the other. Most suitably the tube is supported adjacent one end, to provide an extended length not materially greater than that of the first increment to be reduced, and the die is advanced, over the end to reduce that extended portion, as just described. Thereafter the support point of the tube may be shifted to provide another extended short length for reduction by the die. This cyclic incremental re- I duction is repeated to complete reduction of the article.

I now prefer, however, to operate by the method now to be described.

According to this embodiment a die ring, the diameter of the bore of which is smaller than the outer diameter of the tube to be worked, is

reciprocated relatively to the tube to be reduced while the latter is supported rigidly by any suitable gripping device, whereby a portion of the tube is reduced in diameter, the die is then retracted and the tube or other hollow article is concurrently released andadvanced toward the die ring, either during or after it is returned to its initial position, thus presenting another length of the tube to the die which is reciprocated again relatively to the tube which is again held rigidly by the gripping device. Thereby a successive portion of the tube is reduced in diameter. The cycle is repeated until the entire tube, or any desired part of the tube, is brought to the reduced diameter.

This embodiment is schematically shown in the accompanying drawing. Fig. 1 is a schematic sectional view'of the main partsof the apparatus in the position after tube I has been inserted in gripping means 2 adapted to hold the tube against longitudinal movement when the die is acting on it. The die ring 3, reciprocated by any suitable drive, for instance a crank, not shown, is shown in its initial position. Thegripping mechanism 2 mounted on the machine frame is open so that the tube to be worked can be passed through until it contacts, or is adjacent, die ring 3. Fig. 2 is a view similar to Fig. 1 showing the gripping mechanism 2 closed; the die is then advanced to reduce a short length la of the tube, as seen in Fig. 3, in which die ring 3 has nearly finished its forward stroke with the gripping device still closed. Fi .4 shows the parts of the/apparatus and the tube in the position after the die ring has finished its return stroke, as the, gripping device 2 opens immediately before or after the die ring has finished its forward stroke, the tube is carried on to the left by the die ring by means of the frictional grip of the latter on the tube while the die ring is executing its back stroke. Immediately before the die ring begins a new forward stroke, gripping mechanism 2 is again closed so that the die ring will reduce, at its new forward stroke, the diameter of a successive portion of the tube as shown in Fig. 5.

The intermittent gripping and releasing of the tubes at the intervals when the die ring changes the direction of its motion may easily be performed with well known means.

Besides thesavings obtained by avoiding the forging of points onto the tubes and the waste connected therewith,'a further advantage of the method according to the invention consists in the ability to considerably increase production as compared with that obtained by the known common drawing process, as the method can be performed by using a very high number (e. g., 300 and more) of strokes a minute.

A further advantage of the method according to the invention is that tubes in almost unlimited lengths can be reduced in diameter on an apparatus of very small length and comparatively small weight while with the known drawing process the lengths of the tubes to be reduced are dependent upon the length of the drawingbench. Moreover, the apparatus necessary for the practice of the invention is small and relatively simple.

and described what I now consider to be its best embodiment. However, I desire to have it"understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. That method of reducing the diameter of a hollow metal article which comprises the steps of deflecting the wall of the article toward its longitudinal axis progressively over a short length of the article and in a direction toward the unreduced portion, gripping said unreduced portion, and repeating such progressive deflection of the wall along such short lengths, the said gripping taking efiect at a place not far removed from the place where deflection begins.

2. That method of reducing the diameter of a hollow metal article which comprises the steps of progressively die-reducing the diameter of the article over a relatively short length in a direction toward the unreduced portion, gripping said unreduced portion, interrupting the said die-reduction upon completing reduction of said length, andrepeating such incremental die-reduction to reduce continuously successive lengths of the article, the said gripping taking effect at a. place not far removed from the place where reduction begins.

3. That method of reducing the diameter of a hollow metal article which. comprises the steps of supporting the article as one member and a reducing die as another member relative to one another, successively advancing one of said members relative to the other in intermittent steps to cause die-reduction of successive relatively short lengths of the article in a direction toward its unreduced portion, gripping said unreduced portion, and continuing such intermittent stepwise die-reduction to' progressively reduce continuously successive lengths of the article, the said gripping taking effect at a place not far removed from the place where reduction begins.

4. That method of reducing the diameter of a hollow metal article which comprises the steps of supporting the article rigidly by gripping it adjacent an end thereof at an unreduced portion, advancing a reducing die over said end to thereby'reduce a relatively short length progressively in a direction toward the unreduced portion, shifting the point of support of the article farther toward the unreduced portion to'provide a further relatively short unreduced length, advancing the die over said further length, and repeating such steps to progressively reduce continuously successive lengths of the article.

5. That method of reducing the diameter of a hollow metal article which comprises the steps of supporting the article rigidly at an unreduced portion adjacent an end thereof by external gripping means, advancing a reducing die over said end to progressively reduce a relatively short length in a direction toward the unreduced portion, retracting the die and advancing the tube to provide an unreduced relatively short length ahead of the supported portion, and re- I peating said steps to progressively reduce continuously successive relatively short lengths of the article.

6. That method of reducing the diameter of a "hollow metal article which-comprises the steps of supporting the article rigidly adjacent an end thereof, advancing a reducing die over said end to progressively reduce a relatively short length in a direction toward the unreduced portion, retracting the die and using the frictional grip of the die on the tube for advancing the tube to provide an unreduced relatively short length ahead of the supported portion, and repeating said steps to progressively reduce continuously successive relatively short lengths of the article,

-said supporting. taking place on unreduced sections of the tube.

7. That method of'reducing the diameter of a metal tube which comprises the steps of gripping the tube along its exterior surface at an unreduced portion, deflectingthe wall of the tube toward its longitudinal axis progressively over a short length of the tube and in a direction toward the gripping mechanism, and repeating such progressive deflection of the wall along such short lengths, the said gripping taking eilfect at a place not far 'removed from the place where deflection begins.

8. That method of reducing the diameter of a hollow metal tube which comprises steps of gripping the tube along its exterior surface by mechanical means at an unreduced portion adjacent a reducing die with a relatively short increment of the tube between the gripping mechanism and the die, advancing one of said members relative to the other in a direction toward the unreduced portion, and repeating the 'resultant incremental die reduction to continuously reduce successive lengths of the article. 9. The method of claim 8 in which the gripping mechanism is adapted to open afteneach increment of reduction and the unreduced portion of the tube is fed forward through said a reciprocating die which comprises the steps mechanism by retracting the die and using the frictional grip of the die as the means for advancing said tube.

10. A method of reducing the diameter of a hollow metal tube which consists in gripping an unreduced portion of said tube adjacent an end thereof with an external stationary, releaseable gripping mechanism, forcing a die of substantially smaller internal diameter than the outer diameter of thetube over the free unreduced end of the tube adjacent said gripping mechanism whereby to reducev the diameter of a relatively short length of the tube in a direction toward the unreduced portion, releasing the gripping mechanism without displacing same in relation to the axis of the tube, retracting the die a short interval while maintaining the gripping mechanism stationary and using the frictional grip of the die on the reduced portion of the tube to pull another short increment of the unreduced portion through the gripping mechanism, closing the gripping mechanism on the tube and holding it stationary, again forcing the die over an increment of the imreduced portion toward the stationary gripping mechanism, and repeating the series of operations continuously until the tube has been reduced.

11. That improvement in the method of reducing the diameter of a metal tube or hollow article throughout its entire length by means of of reducing the diameter during movement of the die in one direction while gripping the same at an unreduced portion thereof and feeding the tube or article during movement of the die in the opposite direction by vsaid die, and repeating the operation throughout the entire length of the tube or article.

12. A method according to claim 11 in which the work bench usedfor reducing the diameter of the article is shorter]v than the article to be reduced.

13. That improvement in the method of reducing the diameter ot'a metal tube or hollow article throughout its'entire length bymeans of a reciprocal die and a stationary gripping element which comprises the steps of reducing the diameter of the tube or article by movement of the die in one direction while gripping the tube or article at an unreducd'portion thereof by the stationary gripping element, and feeding the tube or article by the frictional grip of the die during movement of the die in the opposite direction, the die being thus adapted to reduce and feed the tube or article which is intermittently gripped by the gripping element, and repeating the operation throughout the entire length of the tube or article.

FRITZ SINGER. 

